The idea that dropping your arm slot is just for funky relievers or low-velo guys is outdated. New research shows that changing your slot might not just influence deception — it could actually make you more efficient and less stressed at the joint level.

This study examined elite collegiate pitchers to evaluate how different arm slots affect biomechanics — including elbow and shoulder stress, trunk positioning, and torque efficiency — all while tracking velocity across delivery styles.

What they found is simple: you don’t have to throw over the top to throw hard — and you might be healthier if you don’t.

What the Study Found

• Overhand pitchers had the highest elbow varus torque [6.7 % body weight * body height], while sidearm pitchers had the lowest [6.0 % BW*BH] (p = 0.006).
  
  
• Torque efficiency was highest in sidearm pitchers, who generated more velocity per unit of elbow and shoulder torque than other groups (p = 0.003 and p = 0.004, respectively).
  
  
• Shoulder internal rotation torque followed a similar pattern — higher in overhand pitchers [6.6 % BWBH] than sidearm throwers [5.8 % BWBH] (p = 0.012).
  
  
• Trunk side bend was greatest in overhand pitchers at release (–23°), compared to –12° in sidearm pitchers (p = 0.002).
  
  
• Trunk forward flexion was also more extreme in overhand throwers (39° vs. 26° in sidearm, p = 0.028).
  
  
• Throwing velocity was not significantly different across groups (p = 0.668), averaging 86.3 mph.
  
  

Why This Matters

This study is one of the clearest biomechanical cases in support of slot optimization — not just for performance, but for longevity.

While velocity stayed consistent across all groups, overhand throwers absorbed more stress at both the elbow and shoulder and did so with less torque efficiency. That means more force was required to generate the same output. This combination — higher stress, lower efficiency — is a red flag for long-term durability.

The mechanics behind it make sense. Overhand pitchers displayed more extreme lateral trunk tilt and forward flexion, likely increasing joint angles that expose the medial elbow and posterior shoulder to greater load. By contrast, sidearm pitchers were more upright and less tilted at release — biomechanically favoring lower joint stress.

It’s important to clarify that this study doesn’t claim everyone should throw sidearm. Slot selection is a complex blend of anatomy, intention, and movement signature. But it does show that arm slot is a legitimate lever for managing load — and one that doesn’t cost velocity.

How We Apply This at VeloU

At VeloU, we don’t view arm slot as a standalone variable — we see it as the result of rotational strategy, posture, and scapular control.

What many call “arm slot” is really just a byproduct of how the trunk and torso are oriented during rotation. Pitchers with higher slots tend to rely more on extension and flexion patterns — arching into layback and then flexing violently forward. These sagittal-dominant movers generate force through a levered catapult action. In contrast, lower-slot pitchers typically rotate through the transverse plane, staying more stacked and rotating around the spine — which often results in a flatter arm path and more horizontal trunk posture.

That’s why we assess posture and movement signatures before we ever think about “changing” someone’s slot.

We also evaluate scapular function — especially upward rotation and posterior tilt. Higher arm slots demand clean upward rotation of the scapula to get the arm into a safe and powerful position. If an athlete lacks that capability, forcing a high slot becomes a mechanical liability — often leading to elevated joint stress or compensatory trunk mechanics.

This study reinforces our belief that slot changes aren’t cosmetic. They’re mechanical outcomes tied to deeper movement patterns. Rather than chase a one-size-fits-all solution, we match the slot to the athlete — not the other way around.

This article is part of Applied Baseball Science by Dr. Nicholas Serio, where we break down the biomechanics, performance science, and injury research shaping the modern game. Powered by VeloU (Velo University) — where research meets real-world baseball.

Reference

Nagami, T., Susa, K., Hashimoto, K., Yuki, K., & Yanagisawa, O. (2024). Arm slot angle affects joint torque and throwing efficiency in baseball pitchers. Journal of Shoulder and Elbow Surgery, 33(5), 972–979. https://doi.org/10.1016/j.jse.2024.01.017